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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 9 June 2014 by greenman3610

It’s not often that a scientific research paper generates the kind of media attention and scientific community buzz that resulted from a recent study on the apparent inevitability of substantial Antarctic glacial melting.

The early May research headed by lead author Eric Rignot of NASA called attention to melting now under way in Antarctica that CBS News anchor Scott Pelley reported “cannot be stopped.”

Rignot cautioned that the research indicates “we’ve passed the point of no return … It’s just a matter of time before these glaciers disappear to the sea.” While he indicated that the full melt, at the current pace, might not occur for two centuries, he pointed too to evidence suggesting the likelihood of an accelerating pace.

“There’s probably nothing that can be done to stop this,” Rignot said.

“This is really happening,” lead NASA lead polar ice researcher Tom Wagner said. “This weak underbelly of Antarctica is in fact starting to float out into the sea, and there’s not a lot to hold it back.”

A “This is Not Cool” video on the report by independent videographer Peter Sinclair is the first to be posted under the new Yale Climate Connections name, formerly The Yale Forum on Climate Change & The Media. The official transition to that newly named site is to get underway over the next few weeks, initially with a largely cosmetic rebranding, then to be followed by a substantial overhaul and a more multi-media emphasis aimed at better reaching the general public.

Note: link to the Guardian piece referenced in the video is here. Errata – I neglected to thank the European Space Agency for important video animations. Deepest apologies.

“Conventional thinking based on past research is that the Antarctic Ice Sheet has been relatively stable since the last ice age, that it began to melt relatively late during the deglaciation process, and that its decline was slow and steady until it reached its present size,” said lead author Michael Weber, a scientist from the University of Cologne in Germany.

“The sediment record suggests a different pattern — one that is more episodic and suggests that parts of the ice sheet repeatedly became unstable during the last deglaciation,” Weber added.

The research also provides the first solid evidence that the Antarctic Ice Sheet contributed to what is known as meltwater pulse 1A, a period of very rapid sea level rise that began some 14,500 years ago, according to Peter Clark, an Oregon State University paleoclimatologist and co-author on the study.

The largest of the eight episodic pulses outlined in the new Nature study coincides with meltwater pulse 1A.

“During that time, the sea level on a global basis rose about 50 feet in just 350 years — or about 20 times faster than sea level rise over the last century,” noted Clark, a professor in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences. “We don’t yet know what triggered these eight episodes or pulses, but it appears that once the melting of the ice sheet began it was amplified by physical processes.”

The researchers suspect that a feedback mechanism may have accelerated the melting, possibly by changing ocean circulation that brought warmer water to the Antarctic subsurface, according to co-author Axel Timmermann, a climate researcher at the University of Hawaii at Manoa.

Some 9,000 years ago, the episodic pulses of melting stopped, the researchers say.

“Just as we are unsure of what triggered these eight pulses,” Clark said, “we don’t know why they stopped. Perhaps the sheet ran out of ice that was vulnerable to the physical changes that were taking place. However, our new results suggest that the Antarctic Ice Sheet is more unstable than previously considered.”

Comments

Thanks for this great coverage of this important story, especially for emphasizing that the 200+ year timeline much mentioned in most sources assumes a linear development, which is not likely in a feedback system.

Here's an essay on the history of some of these issues, along with a short video: https://etherwave.wordpress.com/2014/05/22/a-historical-primer-on-wais-collapse-part-1-early-history/#comment-7466

It's the other end of the world, but about 10 cubic kilometers of ice seem to have just fallen off of Jakobshavn. This is a very major calving event! Reported on here: http://robertscribbler.wordpress.com/2014/06/06/ten-cubic-kilometers-of-ice-lost-from-jakobshavn-glacier-in-less-than-one-month/#comments

and discussed here:http://forum.arctic-sea-ice.net/index.php/topic,154.200.html

It is clear now that the current IPCC sea level rise projections have significantly underestimated what will be. What Rignot did not show was how continual warming and surface wind dynamics will further exacerbate the mass loss trend, though he alludes to it when mentioning the less-studied east Antarctic ice shelf.

These are all connected and feed back to each other, as does the PIOMAS analysis which projects total summer ice loss of Arctic sea ice within the next 20 years. Sks has done a great job showing how the current IPCC models have overestimated arctic sea ice persistance by 30 years or more.

While it is obscure, the loss of arctic sea ice will lead to a significant see-saw effect on WAIS mass loss rates, combine this with this recent tipping point analysis and the 30-year acceleration in permafrost methane release and our current Integrated Assessment Models have dramatically underestimated the social cost of carbon.

To put that "10 cubic kilometers of ice in 3 months" into perspective: 10km3 = 10Gt. But the total Greenland melt rate is currently approaching 300Gt/y. So, depending on your point of view, either the reported melt is minor (some 10%) on the global scale, or the global scale is so big as to be unimaginable: dwarves even the "entire mountain range".

Good points, chris (though I assume you meant "10 cubic kilometers in less than a month times three months of melting season" = about 30 Gt or 10%.

But that's through one mechanism of ice loss from one location on a very large island. Does anyone have estimates of how much is generally lost these days through calving annually, versus surface melt>evaporation and surface melt> runoff, versus subshelf melt?

Humans have been on a path of destroying this planet since the first tree was cut down and fire was used to burn wooded areas to drive out creatures to be captured for food. It is not surprising that the West Antarctic Ice Sheet is being destroyed by humans spewing forth greenhouse gases and causing the planet to warm. Greenland is also past the 'tipping point' and glaciers are disappearing from the land. Humans that depend on glacial meltwater for sustenance and that live near coasts will be displaced and will have to move elsewhere. And denialists call us "alarmists." Personally, I am alarmed, but more than that, I am furious at politicians and the people who elect them who deny that the planet is in serious trouble.

Though it violates at least two conditions of posting from the comments policy (off topic, no ad hominens, and probably no sloganeering), it would be nice if 4hulkzx10r's comment @7 were not deleted by the moderators. It is a prime example of the idiocy and the conspiratorial nature of many denier posts. In this case the amount of advertising at SkS can be seen in the lefthand side bar, consisting of notices of four books of which John Cook is the author, one of which can be downloaded for free. This contrasts, for example, with WUWT, which has adds for heartland, for Watts' comercial enterprise, for three books of which Watts is not the author, for two types of home meteorological equipment, and for WUWT merchandising in the side bar, plus a purely commercial video add at the head of the blog roll. Prima facie, Watts does generate a commercial return from his blog, while John Cook certainly does not - but we still get lamebrain deniers accusing Cook of being in it for the money, while ignoring the clear commercial interest from denial for many of the more noted deniers.

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Moderator Response:

[PS] Nope. I dont think the comment contributes in any way to the debate. 4hulkzx10r either hasnt bothered to read the comments policy or doesnt care - and as you point out, certainly has nothing useful to contribute to the discussion based on that post.

A agree with both yourself and [PS]. The comment by '4hulkzx10r' belongs to "Deleted Comments".

<snip>

If you want to show that comment as the exemplary, then better solution would be to allow access to Deleted Comments for general users. Currently only admins who delete the comments can see Deleted Comments section. I see a benefit why general public could see it (in read only mode of course): they would better appreciate the good work admins are doing to keep this site nice and clean.

Back to the topic of "unstopable AIS". It's the question of both feasibility & timeframe. The timeframe is probably not just 200y (as mentioned in 4:55, I don't know where greenman took it from) but a bit more. I think I've seen estimates from 200 to 900y. An Eric Rignon said on NASA website:

This sector will be a major contributor to sea level rise in the decades and centuries to come," Rignot said. "A conservative estimate is it could take several centuries for all of the ice to flow into the sea."

Now about feaibility. What would it take to "stop it"? The obvious answer is: reverse the TOA energy imbalance (from 0.7Wm-2 now to say -0.5Wm-2) and wait long enough (50, 100, 200 years?) for ocean to cool enough so that the ice sheet hysteresis response go back towards ice formation. Of course easier said than done: probably physically impossible within next couple centuries with all that persitent CO2, that's why Eric concludes it "unstoppable". The ocean inertia and IS response hysteresis are "blessing in disguise" because they are slowing the surface warming but it turns out very deceitful, especially to the most vulnerable comunities (i.e. the low lying island nations in this case).

Chriskoz, you state the total Greenland land ice melt is now approaching 300Gt per year. Last Data I read was 47 cu miles per year (~200 Gt) and that 47 was from a cherry picked worst year. Antarctica was losing 33 cu mi per year recently for a total of 80 cu miles for both land areas combined. Greenland has 2.85 million km3 and Antarctica has 7.2 million km3 of land ice. Why isn't 10 km3 called out as a 'look..squirrel". Lake Superior added 50 km3 of new ice this past winter, formed since January, and it was finally all melted on June 12.

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Moderator Response:

[PS] "look squirrel" is adding a distracting comment as rhetorical device rather than addressing the arguments made to you. I note that you have clearly read my request for acknowledgement on your past comments but have chosen to ignore it. Obviously that is your choice but your behaviour is then more consistent with trolling rather an search for truth.

"From the end of April 2012 through the end of April 2013, which corresponds reasonably well to the period between the beginning of the 2012 and 2013 melt seasons, the cumulative ice sheet loss was 570 Gt, over twice the average annual loss rate of 260 Gt y-1 during 2003-2012. The 2012-2013 mass loss is the largest annual loss rate for Greenland in the GRACE record, mostly reflecting the large mass loss during the summer of 2012 (Tedesco et al. 2013b). The mass loss during the 2013 summer melt season is likely to be considerably smaller than during 2012, based on other evidence such as the reduced surface melt extent, surface mass balance and runoff described above. A lower mass loss during summer 2013 can also be inferred from the much smaller difference between the April (blue asterisks) and July 2013 mass values (orange asterisks), particularly relative to each of the three previous years (Fig. 56)."

So, you understate last years mass loss by 65%. Your correctly note that it was a record year, but fail to note the average annual loss is 30% greater than the level you claim was record. You try to distract use from the point by pointing to the total mass of ice in Greenland (which has no bearing on the annual increase in sea level from ice melt), but fail to note that the ice melt will accelerate with rising temperatures. Finally you attempt distraction again with an irrelevant comparison to a seasonal fluctuation in floating ice, which therefore (for three reasons) has no bearing on current or future sea level rise.

Should we just assume massive factual errors and irrelevant comments every time you post - or did you set out to excell yourself this time?

You do seem to be quoting figures that are badly wrong. The "last data you read" on Greenland ice loss (possibly from Wikipedia) is a decade out of date. As the rate is markedly accelerating (graphed here), the numbers you quote are far far too low for an up-to-date value.

I'm not familiar with any source, past or present, claiming ice loss from Antarctic sheets at 33 cu miles/yr. Antarctic values are proving more difficult to nail down than Greenland's & the latest numbers have revised the figure downwards by a considerable amount (eg Sasgen et al (2013) or Williams et al (2014)) giving average values of 50-60 cu km/yr for the period 2003-13, but noting that the loss is acceleration and so today it would be roughly 100 cu km/yr = 24 cu mile/yr.

I am also not familiar with the annual ice volumes on Lake Superior. Is there any reason why a few tens of sq km of seasonal ice on that lake would register above "look squirrel" given there is 16,000 sq km seasonal melt of Arctic Sea Ice which has zero significance in this discussion?

I note that, once again, Jetfuel made assertions based on data that were not sourced. When others look at the existing data, and reference them, they see a very different picture. This has happened repeatedly. Just saying.

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Moderator Response:

[PS] Good point. I am guessing Jetfuel is accessing disinformation sites without much skepticism, but then correcting disinformation is what this site exists for.

Jetfuel - can you share what source you used?

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